Many industrial products and processes are limited because of restraints relating to the mechanical and/or chemical properties of component parts. For example, turbine engines would operate more efficiently if the component parts had longer life at higher temperatures. Also, the processing of products, such as chemicals would be more efficient if the component parts of the processing apparatus were more resistant to corrosion and/or high-temperature exposures.
The nickel-base alloys in the art do not meet all the needs of the industry because of many deficiencies in corrosion and mechanical properties. For this reason, many nickel-base alloys must be designed to meet these needs. The differences among new nickel-base alloys may be slight, or even subtle, as they often must be developed to possess certain combinations of properties as required under specific conditions of use.
Table 1 lists a number of alloys in prior art patents. All compositions given in this specification and in the claims are in percent by weight (wt/o) unless otherwise specified. Each of the alloys generally provides excellent corrosion resistance or excellent weld ductility or excellent Charpy impact strength or excellent age hardening characteristics. Some of the alloys may provide more than one of these properties; however, none provides a good combination of all these properties. The compositions of prior art nickel-base alloys in Table 1 nearly all may contain, among other elements, chromium, copper, molybdenum and silicon. For the most part, the alloys are limited for use as castings because of the combined high chromium, silicon, carbon, and copper contents.
There has remained a need for alloys that successfully resist the precipitation of carbide and intermetallic phases while still providing the wide range of corrosion resistance to highly oxidizing conditions in the solution annealed condition. Prior art alloys do not offer sufficient corrosion resistance in some highly oxidizing environments.